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Resistance of catalytic materials towards chemical impurities:the effect of sulphur and biomaterial-based compounds on the performance of DOC and SCR catalystsVäliheikki, A. (Ari) 30 August 2016 (has links)
Abstract
Exhaust gas emissions, e.g. nitrogen oxides (NOx), hydrocarbons (HCs) and carbon monoxide (CO), are harmful to human health and the environment. Catalysis is an efficient method to decrease these emissions. Unfortunately, the fuels and lubricant oils may contain chemical impurities that are also present in exhaust gases. Thus, catalytic materials with high activity and chemical resistance towards impurities are needed in the abatement of exhaust gas emission.
In this thesis, the aim was to gain new knowledge about the effects of chemical impurities on the behaviour and activity of the catalysts. To find out these effects, the impurities existing in the exhaust gas particulate matter after combustion of biofuels and fossil fuels were analysed. The studied zeolite (ZSM-5), cerium-zirconium mixed oxides (CeZr and ZrCe) and silicon-zirconium oxide (SiZr) based catalysts were also treated with impurities to simulate the poisoning of the catalysts by, e.g. potassium, sodium, phosphorus and sulphur, using gas or liquid phase treatments. Several characterization techniques were applied to find out the effects of impurities on catalysts’ properties. The activity of catalysts was tested in laboratory-scale measurements in CO and HC oxidation and NOx reduction using ammonia (NH3) and hydrogen (H2) as reductants.
The results revealed that the CeZr based catalysts had a high activity in NOx reduction by NH3 and moderate activity by H2. Sulphur was proven to enhance the activity of CeZr catalysts in NOx reduction. This is due to an increase in chemisorbed oxygen after the sulphur treatment on the catalyst surface. Instead, in HC and CO oxidation reactions, sulphur had a negligible impact on the activity of the SiZr based diesel oxidation catalyst. Thus, both CeZr and SiZr based catalysts can be utilized in exhaust gas purification when sulphur is present. ZSM-5 based catalysts were proven to be resistant to potassium and sodium. Alternatively, the activity of SiZr based catalysts decreased due to phosphorus. Thus, the removal of biomaterial-based impurities from the exhaust gases is needed to retain high catalyst activity in the exhaust gas after-treatment system. / Tiivistelmä
Pakokaasupäästöissä olevat typen oksidit (NOx), hiilivedyt (HCs) ja hiilimonoksidi (CO) ovat haitallisia ihmisten terveydelle ja ympäristölle. Katalyysi on tehokas menetelmä vähentää näitä päästökomponentteja. Polttoaineet ja voiteluöljyt sisältävät epäpuhtauksia, jotka siirtyvät myös pakokaasuihin. Tästä johtuen pakokaasupäästöjen hallinnassa tarvitaan katalyyttimateriaaleja, joilla on hyvä vastustuskyky myrkyttymistä vastaan.
Tavoitteena oli saada uutta tietoa kemiallisten epäpuhtauksien vaikutuksesta katalyyttien toimintaan. Biopolttoaineiden sisältämät mahdolliset epäpuhtaudet selvitettiin analysoimalla fossiilisen ja biopolttoaineen palamisessa muodostuvia partikkeleita ja vertaamalla niitä polttoaineiden hivenaineanalyysiin. Tutkimuksessa käytetyt zeoliitti (ZSM-5), cerium-zirkonium-sekaoksidi (CeZr) ja pii-zirkonium-oksidipohjaiset (SiZr) katalyytit käsiteltiin epäpuhtauksilla (kalium, natrium, fosfori ja rikki) kaasu- ja nestefaasissa. Tutkimuksessa käytettiin useita karakterisointitekniikoita, joiden avulla selvitettiin epäpuhtauksien vaikutuksia katalyyttien ominaisuuksiin. Katalyyttien toimintaa testattiin laboratoriomittakaavan kokeissa CO:n ja HC-yhdisteiden hapetuksessa sekä NOx:ien pelkistyksessä käyttäen ammoniakkia (NH3) tai vetyä (H2) pelkistimenä.
Tulokset osoittavat, että CeZr-pohjaisten katalyyttien aktiivisuus NOx:ien pelkistyksessä oli hyvä käytettäessä pelkistimenä NH3:a ja kohtalainen käytettäessä vetyä. Rikki paransi CeZr-katalyyttien aktiivisuutta NOx:ien pelkistyksessä, mikä johtui kemiallisesti sitoutuneen hapen osuudesta katalyyttien pinnoilla. Vastaavasti hiilivetyjen ja CO:n hapetusreaktioissa rikki ei vaikuttanut SiZr-pohjaisten dieselhapetuskatalyyttien aktiivisuuteen. Sekä CeZr- ja SiZr-pohjaisia katalyytteja voidaan siten käyttää rikkiä sisältävien pakokaasujen puhdistuksessa. SiZr-pohjaisten katalyyttien aktiivisuus laski fosforin vuoksi. ZSM-5-pohjaiset katalyytit olivat vastustuskykyisiä kaliumille ja natriumille. Kestäviä katalyyttejä on siten kehitettävä, mikäli biopolttoaineiden sisältämien epäpuhtauksien poistaminen polttoaineista ei ole mahdollista.
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A qualitative investigation into the lived experience of psychosocial assessment following self-harmHunter, Cheryl Anne January 2011 (has links)
This thesis investigated the experience of taking part in a psychosocial assessment following an episode of self-harm from the service user perspective. Psychosocial assessments are a key aspect of self-harm management in secondary care, designed to identify needs and risk and determine further care. This study utilised interpretative phenomenological analysis to privilege the voices of service users and produce in-depth, contextualised understandings of the experience of assessment and its impact on future help-seeking and engagement with services. Data collection consisted of semi-structured interviews with thirteen participants soon after their hospital attendance; follow-up semi-structured interviews were also completed with seven participants three months later, to explore patient-derived outcomes from assessment and hospital attendance. The lived experiences of participants were characterised by two main features: experiences of life as a struggle and of the self as “less than”. As a result of these struggles and experiences of powerlessness and devaluation, participants mostly saw self-harm and suicide as a natural progression in their narratives. Expressions of suicidal intent reflected a struggle between a desperate desire for change and hopelessness in the face of current circumstances. The key message gained from participants’ accounts of assessment was that the interaction with staff had the power to reinforce or challenge hopelessness and negative self-evaluations. In addition, the way an assessment was conducted had influence beyond the hospital: as an experience which created or reinforced expectations for future instances of help-seeking; as a deterrent or an encouragement to seek help; and as the first step along the path to change. Unfortunately, participants’ experiences of aftercare were dominated by a sense of stagnation due to the failure of services to follow through with promises of aftercare, which affected their attitudes towards future help-seeking and towards themselves. This thesis is the first study to utilise an in-depth idiographic methodology to explore and contextualise the service user experience of psychosocial assessment following self-harm within the wider circumstances of their lives. It demonstrates how patient-staff interactions within the hospital and after discharge can affect future help-seeking through reinforcing or challenging the hopelessness and self-negativity of patients.
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Cromatografia em fase gasosa como técnica de triagem para diagnóstico laboratorial das intoxicações agudas por medicamentos depressores do sistema nervoso central (OU) Cromatografia em fase gasosa como técnica de triagem para diagnóstico laboratorial das intoxicações agudas por medicamentos que causam síndrome de depressores do sistema nervoso central / Capillary gas chromatography screening for diagnosis of acute poisoning by drugs that cause depression syndromeMello, Sueli Moreira de 05 December 1997 (has links)
A estatística das principais causas das intoxicações mostra que os depressores do sistema nervoso central (SNC) têm uma participação significativa. No Centro de Controle de Intoxicações da Unicamp, em 1995, 30% das intoxicações foram por medicamentos, sendo a metade por depressores do SNC. A avaliação do paciente intoxicado, freqüentemente inclui, além de exames clínicos, análises laboratoriais para identificação de agentes tóxicos presentes em amostras biológicas. Os procedimentos analíticos com esta finalidade utilizam diversas técnicas, entre elas as cromatográficas. O objetivo do presente trabalho foi desenvolver e otimizar um método de triagem para diagnóstico laboratorial das intoxicações por medicamentos que causam depressão do SNC, através da cromatografia em fase gasosa, para ser utilizado em análises de urgência em Centros de Controle de Intoxicações. Foram selecionados 21 fármacos depressores do SNC a partir de critérios de freqüência e importância clínico-toxicológica. As técnicas de extração apresentaram recuperação relativa entre 66,4 e 92,6% para a urina e entre 36,7 e 82,6% para o plasma. O estudo de precisão apresentou coeficiente de variação entre 4,3 e 13,7% para as amostras de urina e entre 7,8 e 19,4% para o plasma. A sensibilidade foi testada para concentrações próximas aos níveis terapêuticos (1 a 5 µg/mL) tendo sido considerada satisfatória e a análise de extratos de \"brancos\" de referência apresentou cromatograma sem interferentes. O tempo de análise foi compatível com a necessidade clínica (menor que duas horas) para análise concomitante dos 21 fármacos. Pode-se concluir que o método de triagem por cromatografia gasosa proposto foi adequado para o diagnóstico laboratorial das intoxicações agudas por medicamentos que causam síndrome de depressão do SNC. / Drugs that cause Central Nervous System Depression Syndrome (CNSDS) have an important role in poisons. At the Poison Control Center of University of Campinas, in 1995, 30% of poisons were due to medicines and a half of that was due to CNS depressants. The evaluation of the poisoned patient includes, in addition to clinical examinations, laboratorial screenings to identify toxic agents in biological samples. The analytical procedures with this endpoint use several methods, including chromatographic analyses. The objective of this study was to develop and to optimize a procedure for screening drugs that cause CNSDS, through gas chromatography, to be used in emergency assays at the Poison Control Center. Twenty one drugs were selected using frequency and clinical-toxicology importance criteria. The extraction technique presented relative recuperation between 66.4 and 92.6% for urine and 36.7 and 82.6% for plasma. The intra-assay coefficient of variation was between 4.3 and 13.7% for urine and 7.8 and 19.4% for plasma. The sensibility was tested for concentrations near therapeutical levels (1 to 5 µg/ml) and was considered satisfactory. The chromatogram of blank sample extract presented no interferences. The time required to screen 21 drugs in plasma and urine samples was less than 2 hours, making this method appropriate for use in poison control center in hospitals.
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Morphologie und Degradation von O2, Pt│YSZ-ElektrodensystemenVonau, Corinna 02 October 2015 (has links)
In der vorliegenden Arbeit wird erstmals systematisch der Einfluss von gasförmigen und festen Verunreinigungen auf das O2, Pt│YSZ- Elektrodensystem am praxisnahen Beispiel der Lambdasonde untersucht. Dazu wurden Festelektrolyt- und Elektrodenmaterialien unterschiedlicher Zusammensetzung und Morphologie den realen Abgasbedingungen nachempfundenen, chemischen und physikalischen Einflüssen ausgesetzt und in Bezug auf Langzeitstabilität, Sensitivität und Wirkmechanismen untersucht. Im Einzelnen lag der Fokus der Untersuchungen auf zwei Ausführungsformen von Elektroden, die sich vor allem durch mikro- bzw. nanoskalige Partikelgrößenverteilungen sowie der Platin/YSZ-Zusammensetzung unterschieden und als Mikro- bzw. Nano-Elektrode bezeichnet wurden.
Der Einfluss von Siliciumdioxid als gezielt dem Festelektrolyten beigemischte intrinsische Vergiftung sollte in Wechselwirkung zu den extrinsischen Verunreinigungen wie Natriumionen, Wasserdampf und Phosphorpentoxid untersucht werden. Im Unterschied zu den in der Literatur betrachteten, vereinfachten Modellsystemen konnten damit erstmals Wechselwirkungen beschrieben werden, die zu einem tieferen Verständnis des realen Sensorverhaltens, vor allem der Degradation beitragen. Insbesondere ist es gelungen, ein Modell für die Sauerstoffreaktion an geschädigten Elektroden aufzustellen. Neben der bekannten elektrochemischen Reduktion von Sauerstoff spielen die Transportvorgänge an der Elektrodenoberfläche eine entscheidende Rolle, über die in der Literatur bisher nur wenig bekannt war.:1 Einleitung
1.1 Motivation
1.2 Zielsetzung
1.3 Methodisches Vorgehen und struktureller Aufbau der Arbeit
2 Theoretische Grundlagen
2.1 Festelektrolyt Yttriumoxid stabilisiertes ZrO2 (YSZ)
2.1.1 Strukturelle Aspekte
2.1.2 Elektronen- und Ionenleitung
2.2 Elektroden im Gleichgewicht und unter Stromfluss
2.2.1 Gleichgewichtselektrode
2.2.2 Elektroden unter Stromfluss
2.2.2.1 Ladungsdurchtritt und Transportprozesse
2.2.2.2 Co-limitierte Prozesse
2.2.2.3 Konzentrationslimitierendes Verhalten
2.3 Stabilität von Elektrodensystemen
2.3.1.1 Unterschiede von dichten und porösen Metall/ Cermet-
Elektroden (morphologische Parameter)
2.3.1.2 Ursachen der Degradation
2.4 Elektrochemische Methodik zur Charakterisierung des Elektrodensystems
2.4.1 Zyklovoltammetrie
2.4.2 Elektrochemische Impedanzuntersuchung
3 Messtechnik und Experimentelles
3.1 Probenherstellung
3.1.1 Präparation und Zusammensetzung
3.1.2 Funktion
3.2 Messplätze für Elektroden- und Sensoruntersuchungen
3.2.1 Standardmessplatz
3.2.2 Messplatz zur Phosphorvergiftung
3.3 Vorbehandlung des Elektrodensystems
3.4 Degradation und Bewertung
3.4.1 Degradation durch SiO2
3.4.2 YSZ-Degradation durch Wasser
3.4.3 YSZ-Degradation durch Natriumionen
3.4.4 Elektrodendegradation durch Wasserdampf
3.4.5 Elektrodendegradation durch Phosphor
3.4.6 Regeneration
3.5 Charakterisierung des Elektrodenystems & Grenzen der Methodik
3.5.1 Analytische und bildgebende Verfahren
3.5.2 Elektrochemische Verfahren
4 Experimentelle Ergebnisse und Diskussion
4.1 Morphologie der Elektrodensysteme
4.1.1 Festelektrolyt
4.1.1.1 Einfluss von Siliciumdioxid
4.1.1.2 Einfluss von Natriumionen
4.1.1.3 Zusammenfassung Festelektrolyt
4.1.2 Poröse Cermet-Elektrode
4.1.2.1 Elektrodenstruktur
4.1.2.2 Elementare Elektrodenprozesse
4.1.2.3 Niedertemperaturverhalten
4.1.2.4 Zusammenfassung der Resultate, gewonnen an der porösen Cermet-Elektrode
4.2 Degradation der Elektrodensysteme
4.2.1 Einfluss von Siliziumdioxid
4.2.2 Einfluss von Wasserdampf
4.2.2.1 Motivation
4.2.2.2 Festelektrolyt
4.2.2.3 Alterung von Cermet-Elektroden in Wasserdampfhaltigen Gasen
4.2.2.4 Elektrochemisch provozierte Reaktionen
4.2.2.5 Degradationsmechanismen
4.2.2.6 Zusammenfassung H2O
4.2.3 Einfluss von Phosphorpentoxid
4.2.3.1 Elektrochemisch provozierte Reaktion
4.2.3.2 Degradationsmechanismen
4.2.3.3 Zusammenfassung P2O5
5 Zusammenfassung und Ausblick
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An Investigation of Target Poisoning during Reactive Magnetron SputteringGüttler, Dominik 12 March 2009 (has links)
Objective of the present work is a broad investigation of the so called "target poisoning" during magnetron deposition of TiN in an Ar/N2 atmosphere. Investigations include realtime in-situ ion beam analysis of nitrogen incorporation at the Ti sputter target during the deposition process and the analysis of particle uxes towards and from the target by means of energy resolved mass spectrometry. For experiments a planar, circular DC magnetron, equipped with a 2 inch titanium target was installed in an ultrahigh vacuum chamber which was attached to the beam line system of a 5 MV tandem accelerator. A manipulator allows to move the magnetron vertically and thereby the lateral investigation of the target surface. During magnetron operation the inert and reactive gas flow were adjusted using mass flow controllers resulting in an operating pressure of about 0.3 Pa. The argon flow was fixed, whereas the nitrogen flow was varied to realize different states of target poisoning. In a fi?rst step the mass spectrometer was used to verify and measure basic plasma properties e.g. the residual gas composition, the behavior of reactive gas partial pressure, the plasma potential and the dissociation degree of reactive gas molecules. Based on the non-uniform appearance of the magnetron discharge further measurements were performed in order to discuss the role of varying particle fluxes across the target during the poisoning process. Energy and yield of sputtered particles were analyzed laterally resolved, which allows to describe the surface composition of the target. The energy resolving mass spectrometer was placed at substrate position and the target surface was scanned by changing the magnetron position correspondingly. It was found, that the obtained energy distributions (EDF) of sputtered particles are influenced by their origin, showing signi?ficant differences between the center and the erosion zone of the target. These results are interpreted in terms of laterally different states of target poisoning, which results in a variation of the surface binding energy. Consequently the observed energy shift of the EDF indicates the metallic or already poisoned fraction on target surface. Furthermore the EDF's obtained in reactive sputtering mode are broadened. Thus a superposition of two components, which correspond to the metallic and compound fractions of the surface, is assumed. The conclusion of this treatment is an discrete variation of surface binding energy during the transition from metallic to compound target composition. The reactive gas target coverage as derived from the sputtered energy distributions is in reasonable agreement with predictions from model calculations. The target uptake of nitrogen was determined by means of ion beam analysis using the 14N(d, )12C nuclear reaction. Measurements at varying nitrogen gas flow directly demonstrate the poisoning eff?ect. The reactive gas uptake saturates at a maximum nitrogen areal density of about 1.1016 cm-2 which corresponds to the stoichiometric limit of a 3 nm TiN layer. At sufficiently low reactive gas flow a scan across the target surface discloses a pronounced lateral variation of target poisoning, with a lower areal density in the target race track compared to the target center and edge. Again the findings are reproduced by model calculations, which confirm that the balance of reactive gas injection and sputter erosion is shifted towards erosion in the race track. Accomplished computer simulations of the reactive sputtering process are similar to Berg's well known model. Though based on experimental findings the algorithm was extended to an analytical two layer model which includes the adsorption of reactive gas as well as its different kinds of implantation. A distribution of ion current density across the target diameter is introduced, which allows a more detailed characterization of the processes at the surface. Experimental results and computer simulation have shown that at sufficiently low reactive gas flow, metallic and compound fractions may exist together on the target surface, which is in contradiction to previous simulations, where a homogeneous reactive gas coverage is assumed. Based on the results the dominant mechanisms of nitrogen incorporation at different target locations and at varying reactive gas admixture were identified. / Gegenstand der Arbeit ist die Untersuchung der Targetvergiftung beim reaktiven Magnetronsputtern von TiN in Argon-Sticksoff Atmosphäre. Die Untersuchungen beinhalten die Echtzeit in-situ Ionenstrahlanalyse des Stickstoffeinbaus in das Titantarget während des Depositionsprozesses sowie die Analyse der Teilchenflüsse vom – und hin zum Sputtertarget mittels energieaufgelöster Massenspektrometrie. Das Magnetron wurde in einer Vakuumkammer installiert, welche an die Beamline des 5 MV Tandembeschleunigers angeschlossen war. Die Position des Magnetrons konnte mittels eines Manipulator verändert werden, was die laterale Untersuchung der Targetoberfläche ermöglichte. Während des Magnetronbetriebes wurde der Argonfluss in die Kammer konstant gehalten, während der Stickstofffluss variiert wurde um verschiedene Ausprägungen der Targetvergiftung zu erreichen. In einem ersten Schritt wurden die Eigenschaften des Plasmas, z.B. die Zusammensetzung des Sputtergases, das Verhalten des Reaktivgaspartialdruckes, das Plasmapotenzial und der Dissoziationsgrad der Reaktivgasmoleküle im Plasma, mit dem Massenspektrometer ermittelt. Aufgrund der ungleichmäßigen Gasentladung vor dem Magnetrontarget, wurden auch lateral variierende Teilchenflüssen und eine ungleichmäßige Targetvergiftung angenommen. Die Energie und die Ausbeute von gesputterten Teilchen wurde deshalb lateral aufgelöst untersucht. Das Massenspektrometer wurde zu diesem Zweck am Ort des Substrates positioniert und die Targetoberfläche konnte gescannt werden indem die Magnetronposition verändert wurde. Die so aufgenommenen Energieverteilungen der gesputterten Teilchen zeigen eine räumliche Abhängigkeit. Teilchen die aus dem Targetzentrum stammen unterscheiden sich hinsichtlich ihrer Energie signifikant von den Teilchen die in der Target-Erosionszone gesputtert werden. Dieses Resultat zeigt die ungleichmäßige Targetvergiftung, wodurch es zu einer Veränderung der Oberflächenbindungsenergie kommt. Über die Verschiebung in der Energieverteilung lässt sich somit der Zustand der Targetoberfläche beschreiben. Diese experimentellen Ergebnisse zeigen Übereinstimmung mit den Ergebnissen der Modellrechnungen. Der Stickstoffgehalt des Targets wurde weiterhin mittels Ionenstrahlanalyse (NRA) bestimmt. Messungen bei verschiedenen Stickstoffflüssen demonstrieren direkt die Vergiftung des Targets. Die maximale Stickstoffkonzentration sättigt bei einem Wert, der dem Stickstoffgehalt in einer ca. 3 nm dicken Titannitridschicht entspricht. Bei ausreichend niedrigem Stickstofffluss zeigt die Messung quer über den Targetdurchmesser eine Variation im Stickstoffgehalt. Die Stickstoffkonzentration in der Erosionszone ist deutlich geringer als im Targetzentrum oder am Targetrand. Die Resultate wurden wiederum durch Modellrechnungen bestätigt. Die durchgeführten Computersimulationen basieren auf Sören Bergs Modell des reaktiven Sputterprozesses. Der Algorithmus wurde jedoch auf der Basis der experimentellen Ergebnisse erweitert. Das Modell beinhaltet nun Mechanismen des Reaktivgaseinbaus in das Target, wie Adsorption, Implantation und Recoilimplantation. Des Weiteren wurde die Ionenstromverteilung als Funktion des Targetdurchmessers in das Modell aufgenommen, was eine detailliertere Beschreibung des Prozesses ermöglicht. Die experimentellen Ergebnisse und die Resultate der Computersimulation zeigen, dass bei niedrigen Reaktivgasflüssen metallische und vergiftete Bereiche auf der Targetoberfläche gemeinsam existieren. Das ist im Widerspruch zu älteren Simulationen, in denen von einer homogenen Targetbedeckung durch das Reaktivgas ausgegangen wird. Basierend auf den Ergebnissen wurden die dominierenden Mechanismen des Reaktivgaseinbaus in das Sputtertarget, in Abhängigkeit von der Position und von der Sputtergaszusammensetzung, identifiziert.
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Verifiering av metod för analys av etylenglykol i plasma på Roche Cobas® c502Lindgren, Rebecca January 2021 (has links)
Etylenglykol (etan-1,2-diol) är en dihydroxyalkohol som är en komponent i kylarvätska och andra frost- och kylskyddsmedel. Förtäring av etylenglykol leder till allvarliga skador och i värsta fall död utan behandling. I Sverige år 2020 fanns det endast ett tiotal laboratorier som erbjöd analys av etylenglykol dygnet runt. Detta leder till att prover ofta behöver skickas till större laboratorier med taxi vilket i sin tur leder till en försenad diagnosticering av patienten. Syftet med examensarbetet var att verifiera en enzymatisk kolorimetrisk metod för analys av etylenglykol i plasma på instrumentet Roche Cobas® 8000 modul c502. Reagenset som verifierades var DiscretPak™ Ethylene Glycol Reagents från företaget Catachem. Verifieringen gjordes med avseende på total precision (repeterbarhet), inomserieprecision och linjäritet. Resultaten jämfördes med analys på gaskromatograf. Provmaterialet bestod av patientprover av litiumheparinplasma, patientprover av serum och kontrollprover från Equalis. Resultatet som erhölls vid verifieringen visade på linjär korrelation mellan den enzymatiska metoden och GC-analys. En negativ bias observerades dock i jämförelse med analys på gaskromatograf. Utvärdering av repeterbarhet gav CV 4,6% vid 9,0 mmol/L och 3,66% vid 40,0 mmol/L. Inomserieprecisionstudie gav CV 14,7% vid 1 mmol/L, 5,2% vid 4 mmol/L och 1,4% vid 17 mmol/L. Precisionen är viktigast vid de lägre koncentrationerna. Insättning av behandling med antidot är aktuellt vid 4 mmol/L. Utvärdering av linjäritet visade på ett starkt linjärt samband hos analysen vid koncentrationer <50 mmol/L. Vid koncentrationer >50 mmol/L fanns ett linjärt samband men en minskad överensstämmelse mellan den beräknade och den uppmätta koncentrationen observerades. Metodverifieringen ansågs vara godkänd för kliniskt bruk och analysen kommer att införas i analyssortimentet hos Klinisk Kemi i Växjö. / Ethylene glycol is an alcohol that is a common component in antifreeze. Ingestion of ethylene glycol will, without treatment, lead to severe organ damage and in worst-case death. In 2020 there was only a few laboratories in Sweden that offered analysis of ethylene glycol all hours of the day and week. This means that samples often need to be transported to laboratories at larger hospitals which leads delayed diagnosis of the patient. The purpose of this study was to verify an enzymatic method for analysis of ethylene glycol in plasma on the instrument Roche Cobas® 8000 module c502. The reagent that was used was DiscretPak™ Ethylene Glycol Reagents from Catachem. The study included evaluation of total precision, within-run precision, linearity, and a comparison with analysis with gas chromatography (GC). The sample material consisted of patient samples of plasma, patient samples of serum and quality controls from Equalis. The result of the study showed linear correlation between the enzymatic method and analysis with GC. A negative bias was observed in comparison to analysis with GC. The coefficient of variation (CV) for total precision was 4,7% at 9,0 mmol/L and 3,7% at 40,0 mmol/L. The CV for within-run was 14,7% at 1 mmol/L, 5,2% at 4 mmol/L and 1,4% at 17 mmol/L. The precision of the method is most important at lower concentrations. The evaluation of linearity showed linear correlation at concentrations <50 mmol/L with. A linear correlation was observed at concentrations >50 mmol/L, although the agreement with the calculated concentrations decreased. The method verification was successful as the results were deemed acceptable for clinical use.
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PREVENTING DATA POISONING ATTACKS IN FEDERATED MACHINE LEARNING BY AN ENCRYPTED VERIFICATION KEYMahdee, Jodayree 06 1900 (has links)
Federated learning has gained attention recently for its ability to protect data privacy and distribute computing loads [1]. It overcomes the limitations of traditional machine learning algorithms by allowing computers to train on remote data inputs and build models while keeping participant privacy intact. Traditional machine learning offered a solution by enabling computers to learn patterns and make decisions from data without explicit programming. It opened up new possibilities for automating tasks, recognizing patterns, and making predictions. With the exponential growth of data and advances in computational power, machine learning has become a powerful tool in various domains, driving innovations in fields such as image recognition, natural language processing, autonomous vehicles, and personalized recommendations. traditional machine learning, data is usually transferred to a central server, raising concerns about privacy and security. Centralizing data exposes sensitive information, making it vulnerable to breaches or unauthorized access.
Centralized machine learning assumes that all data is available at a central location, which is only sometimes practical or feasible. Some data may be distributed across different locations, owned by different entities, or subject to legal or privacy restrictions. Training a global model in traditional machine learning involves frequent communication between the central server and participating devices. This communication overhead can be substantial, particularly when dealing with large-scale datasets or resource-constrained devices. / Recent studies have uncovered security issues with most of the federated learning models. One common false assumption in the federated learning model is that participants are the attacker and would not use polluted data. This vulnerability enables attackers to train their models using polluted data and then send the polluted updates to the training server for aggregation, potentially poisoning the overall model. In such a setting, it is challenging for an edge server to thoroughly inspect the data used for model training and supervise any edge device. This study evaluates the vulnerabilities present in federated learning and explores various types of attacks that can occur. This paper presents a robust prevention scheme to address these vulnerabilities. The proposed prevention scheme enables federated learning servers to monitor participants actively in real-time and identify infected individuals by introducing an encrypted verification scheme. The paper outlines the protocol design of this prevention scheme and presents experimental results that demonstrate its effectiveness. / Thesis / Doctor of Philosophy (PhD) / federated learning models face significant security challenges and can be vulnerable to attacks. For instance, federated learning models assume participants are not attackers and will not manipulate the data. However, in reality, attackers can compromise the data of remote participants by inserting fake or altering existing data, which can result in polluted training results being sent to the server. For instance, if the sample data is an animal image, attackers can modify it to contaminate the training data.
This paper introduces a robust preventive approach to counter data pollution attacks in real-time. It incorporates an encrypted verification scheme into the federated learning model, preventing poisoning attacks without the need for specific attack detection programming. The main contribution of this paper is a mechanism for detection and prevention that allows the training server to supervise real-time training and stop data modifications in each client's storage before and between training rounds. The training server can identify real-time modifications and remove infected remote participants with this scheme.
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Metal exposure estimates in established biomarkers, epigenetic biomarkers, and associations with cardiovascular outcomes in the Strong Heart StudyLieberman-Cribbin, Wil January 2024 (has links)
Cardiovascular disease remains the leading causing of death worldwide. American Indians experience an elevated prevelance of cardiovascular disease (CVD) and chronic metal exposures. Determining the impact of metal exposures on CVD can inform prevention and exposure reduction strategies. This dissertation will advance environmental monitoring and biological monitoring of lead, uranium, and selenium exposures using both established biomarkers and novel epigenetic biomarkers to determine the associations of metals with CVD, leveraging the Strong Heart Study (SHS), a prospective cohort of CVD and its risk factors among American Indian adults from tribes and communities in Arizona, Oklahoma, North Dakota, and South Dakota. In Chapter 1, we discuss lead, uranium, and selenium, sources of exposure, and relevance to cardiovascular disease. This includes an overview of metal toxicokinetics and how we can assess these contaminants in both established biomarkers, including blood and urine, as well as in epigenetic biomarkers.
In Chapter 2, we estimated urinary uranium concentrations from data on uranium in water among Strong Heart Family Study participants. These estimates were derived from relationships between urinary uranium and water uranium assessed in Strong Heart Family Study (SHFS) participants (n=1,356). Predictions were made using generalized linear models and included demographic and clinical participant characteristics in addition to other metal contaminants measured in water and urine. The root mean square error (RMSE) of the prediction model was 1.01, and predicted urine uranium levels were comparable (median: 0.04 μg/g creatinine, 25th-75th: 0.02-0.08 μg/g creatinine) to urine uranium measured in the SHFS (0.04 μg/g creatinine, 0.02-0.07 μg/g creatinine). These findings emphasize the contribution of uranium in water to urine uranium (reflecting internal dose), and demonstrate the relevance of estimating metal contaminants in urine for the SHS to inform relationships with health effects.
In Chapter 3, we evaluated whether urinary uranium concentrations were associated with measures of cardiac geometry and functioning among 1,332 American Indian youth and young adults from the SHFS. Transthoracic echocardiography and blood pressure was assessed at baseline (2001-2003) and a follow-up visit (2006-2009). We estimated mean differences in measures of cardiac geometry and functioning at baseline and follow-up using linear mixed effect models with random intercept and slope over time. In fully adjusted models, a log-doubling of urinary uranium was positively associated with left ventricular (LV) mass index (mean difference: 0.49 g/m2, 95% CI: 0.07-0.92 g/m2), left atrial systolic diameter (0.02 cm, 0.01-0.03 cm), and stroke volume (0.66 mL, 0.25-1.08 mL) at baseline. At follow-up, uranium was associated with increases in left atrial diameter (0.02 cm, 0.01-0.03 cm), pulse pressure (0.28 mmHg, 0.05-0.52 mmHg), and incident LV hypertrophy (OR: 1.25, 95% CI: 1.06, 1.48). These findings support the need to determine the potential long-term clinical and subclinical cardiovascular effects of chronic uranium exposure in the general population, and the need for future strategies to reduce exposure.
In Chapter 4, we evaluated if blood lead was associated with CVD incidence and mortality in 1,818 adult American Indian participants. This study estimated the risk of incident CVD and CVD deaths in models adjusted for demographic, lifestyle, and cardiovascular risk factors. Blood lead levels in American Indian adults were associated with increased risk of CVD and coronary heart disease (CHD) incidence and mortality. The hazard ratio (HR) (95% CI) of mortality per change across the 80th-20th quantiles in blood lead was 1.15 (1.02-1.30) for CVD overall and 1.22 (1.08-1.37) for CHD. The corresponding HR was 1.11 (1.01-1.22) for incident CVD and 1.12 (1.00-1.25) for incident CHD. These findings contribute to the evidence of lead as a CVD risk factor at low levels and highlight the importance of further reducing lead exposure in communities across the United States, including American Indian communities.
In Chapter 5, we leveraged novel epigenetic biomarkers of lead exposure to investigate their association with cardiovascular disease (CVD) incidence and mortality among 2,231 participants of the Strong Heart Study. Blood DNA methylation was measured using the Illumina MethylationEPIC BeadChip at baseline (1989-1991) and epigenetic biomarkers of lead levels in blood, patella, and tibia were estimated using previously developed biomarkers of DNA methylation at specific CpG sites. In adjusted models, the hazard ratio (HR) (95% CI) of CVD mortality per doubling increase in lead epigenetic biomarkers were 1.42 (1.07-1.87) for tibia lead, 1.22 (0.93-1.60) for patella lead, and 1.57 (1.16-2.11) for blood lead. The corresponding HRs for incident CVD were 0.99 (0.83-1.19), 1.07 (0.89-1.29), and 1.06 (0.87-1.30). The association between the tibia lead epigenetic biomarker and CVD mortality was modified by sex (interaction p-value: 0.014), with men at increased risk (HR: 1.42, 95% CI:1.17-1.72) compared to women (HR: 1.04, 95% CI:0.89-1.22). These findings support that epigenetic biomarkers of lead exposure may capture some of the disease risk associated with lead exposure.
In Chapter 6, we investigated the association between urinary selenium levels and DNA methylation (DNAm) among 1,357 participants free of CVD and diabetes in the SHS. Selenium concentrations were measured in urine (collected in 1989-1991) using inductively coupled plasma mass spectrometry. DNAm in whole blood was measured cross-sectionally using the Illumina Methylation EPIC BeadChip (850K) Array. We used epigenome-wide robust linear regressions and elastic net to identify differentially methylated CpG sites associated with urinary selenium levels. Across 788,368 CpG sites, five differentially methylated positions (DMP) (cg00163554, cg18212762, cg25194720, cg11270656, cg00886293) were significantly associated with Se in linear regressions after accounting for multiple comparisons (false discovery rate p-value: 0.10). The top associated DMP (cg00163554) was annotated to the Disco Interacting Protein 2 Homolog C (DIP2C) gene, which relates to transcription factor binding. Future analyses should explore these relationships prospectively and investigate the potential role of differentially methylated sites with disease endpoints.
In Chapter 7, we evaluated if declines in blood lead were associated with changes in systolic and diastolic blood pressure in adult American Indian participants from the SHFS (n=285). Using generalized estimating equations, a significant non-linear association between declines in blood lead and declines in systolic blood pressure was detected, with significant linear associations where blood lead decline was 1 µg/L or higher. These findings suggest the need to further study the cardiovascular impacts of reducing lead exposures and the importance of lead exposure prevention.
In conclusion, we find that established biomarkers of metal exposure reflecting internal dose such as blood and urine, as well as epigenetic biomarkers of metals exposures, were associated with subclinical CVD and CVD incidence and mortality. Findings concerning blood lead emphasize that low levels of lead remain relevant for CVD, and declines in blood lead even when small (1.0-10.0 µg/L), were associated with reductions in systolic blood pressure. Novelly, we present that urinary uranium levels were adversely associated with measures of cardiac geometry and left ventricular functioning among American Indian adults, and that future attention must be paid to investigating associations with subclinical disease. We also find utility in using epigenetic biomarkers to capture CVD risk, as tibia and blood epigenetic biomarkers of lead, were associated with increased risk of CVD mortality, and urinary selenium was associated with distinct changes in DNAm. Although further work must further validate these epigenetic biomarkers in different populations, future work must continue to investigate these epigenetic biomarkers given their potential to capture CVD risk.
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Cotton Mathers's Wonders of the Invisible World: An Authoritative EditionWise, Paul Melvin 12 January 2005 (has links)
ABSTRACT Although Cotton Mather, as the official chronicler of the 1692 Salem witch trials, is infamously associated with those events, and excerpts from his apologia on Salem, Wonders of the Invisible World, are widely anthologized today, no annotated critical edition of the entire work has appeared in print since the nineteenth century. This present edition of Wonders seeks to remedy this lacuna in modern scholarship. In Wonders, Mather applies both his views on witchcraft and on millennialism to events at Salem. This edition to Mather's Wonders presents this seventeenth-century text beside an integrated theory of the initial causes of the Salem witch panic. The juxtaposition of the probable natural causes of Salem's bewitchment with Mather's implausible explanations exposes the disingenuousness of his writing about Salem. My theory of what happened at Salem includes the probability that a group of conspirators led by the Rev. Samuel Parris deliberately orchestrated the "witchcraft" and that a plant, the thorn apple, used in Algonquian initiation rites, caused the initial symptoms of bewitchment (39-189). Furthermore, key spectral evidence used at the Salem witch trials and recorded by Mather in Wonders appears to have been generated by intense nightmares, commonly thought at the time to be witch visitations, resulting from what is today termed sleep paralysis (215-310). This dissertation provides a detailed look at some of the testimony given in the Salem court records and in Wonders of the Invisible World as it relates to the interpretation in folklore of the phenomenology of nightmares associated with sleep paralysis. The third chapter of this dissertation focuses extensively on Mather's text as a disingenuous response to the Salem witch trials (320-456). The final section of chapter three posits a "Scythian" or Eurasian connection between Swedish and Salem witchcraft. Similarities in shamanic practices among respective indigenous populations of Lapland, Eurasia, Asia, and New England, caused the devil's involvement in both the visible and invisible worlds to appear more than theoretical to writers like Jose Acosta, Johannes Scheffer, Nicholas Fuller, Joseph Mede, Anthony Horneck, and Cotton Mather, inducing Mather to include a lengthy abstract of the Swedish account in Wonders (404-449).
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Étude comparative sur les manifestations du genre dans les crimes d’empoisonnement au Québec à la fin du XIXe siècleCourtemanche, Stéphanie 04 1900 (has links)
Au XIXe siècle émerge une criminologie naturalisante qui définit l’empoisonnement
comme un crime féminin. L’étude proposée explore le lien qui s’établit entre le sexe de la
personne criminelle, son genre et le moyen de perpétration de son acte meurtrier par
l’analyse des procès pour empoisonnement répertoriés au Québec pour la période allant
de 1867 à 1900. Comparant les procès d’empoisonneurs aux procès d’empoisonneuses,
confrontant les acteurs historiques à leurs situations vécues, la recherche parcourt les
manifestations du genre dans les méthodes criminelles employées par les accusé-e-s ainsi
que dans les discours produits à leur endroit tout au long du processus judiciaire. Les
résultats sont révélateurs des normes sexuelles en vigueur dans la société québécoise à la
fin de l’époque victorienne et s’insèrent dans la lignée des études sur la régulation sociale
au Québec. / In the nineteenth century emerges a naturalizing criminology which defines poisoning as
a female crime. The proposed study explores the relationship developed between the
gender of the criminal person, the kind and the commission of his murderous act and that,
through the analysis of trials for poisoning listed in Quebec from 1867 to 1900.
Comparing the male poisoners’ trials to the female poisoners’ trials as well as the historic
players to their life situations, the search runs through the events of its kind in the
criminal methods employed by defendants and in the resulting speeches concerning them
throughout the judicial process. The results are indicative of sexual norms in Quebec
society at the end of the Victorian era and fit into the tradition of social regulation studies
in Quebec.
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